1. Field
The present specification generally relates to conductive inks and preparation methods and, in particular, to water-based conductive inks and preparation methods in which elemental contaminants in the conductive inks are present at less than 100 parts per million (ppm).
2. Technical Background
Polymer-based electrically conductive composites such as conductive ink coatings are used for electronic devices such as ultracapacitors. The ink coatings are usually comprised of conductive materials such as expensive carbon fibrils (carbon filaments) that have high surface area and conductance, binders that provide adhesion to a substrate and cohesion between structures, and other additives such as thickeners, conductivity enhancing agents, anti-kogation agents, drying agents and defoamers. A notable limitation in the use of conductive particles in conductive inks, particularly for devices such as ultracapacitors, is faradic reactions. Faradic reactions occur as a result of charge transfer at the surface of an electrode as a result of electrochemical reaction.
There remain ongoing needs for conductive ink compositions and preparation methods that reduce or eliminate faradic reactions in devices in which the conductive ink compositions are used.